Alien::SVN is a wrapper to install the Perl bindings for subversion,
also known as SVN::Core.
If your module needs SVN::Core it can depend on Alien::SVN instead and then the CPAN shell can handle automatic installation.
This is particularly useful for programs like SVK.

It comes with a copy of Subversion 1.6.12 which it will compile but only installs the Perl and Subversion libraries.
The subversion binaries will not be installed.